For what it’s worth, I’ve recently completed the FA referee course, and was told categorically that Grassroots officials are to wear all black, and the team on a dark/black shirt need to wear the bibs/change not the FAMOA.We were advised never to wear bibs as this undermines the authority of the official.
As a note, and I’m not sure if this is an FA rule, in both Dorset and Hampshire leagues, it clearly states that no team is to wear a black or dark coloured kit.
The only exceptions I understand to this rule, are Level 1/2 officials where they might be officiating EFL or EPL football.